#include <stdio.h>
#include <unistd.h>

int global_val = 100;

int main()
{
    pid_t id = fork();
    if (id == 0)
    {
        int cnt = 0;
        while (1)
        {
            printf("我是子进程, pid:%d, ppid:%d, global_val:%d, &global_val:%p\n", getpid(), getppid(), global_val, &global_val);
            sleep(1);
            ++cnt;
            if (cnt == 3)
            {
                global_val = 300;
                printf("子进程已经更改了global_val的值了!\n");
            }
        }
    }
    while (1)
    {
        printf("我是父进程, pid:%d, ppid:%d, global_val:%d, &global_val:%p\n", getpid(), getppid(), global_val, &global_val);
        sleep(1);
    }
    return 0;
}